Cylinder head for internal combustion engines



A. SCHWARZ Dec. 13, 1938.

CYLINDER HEAD FOR INTERNAL COMBUSTION ENGINES Filed July 22, 1956 2Sheet-Sheet 1 ATTORN EY Dec. 13, 1938. A. SCHWARZ 2,

CYLINDER HEAD FOR INTERNAL COMBUSTION ENGINES Filed July 22, 1936 2SIneets-$heet 2 INVENTOR A? red \Schu/arz BY M ATTORNEY Patented Dec.13, 1938 UNITED; STATES PATENT OFFICE CYLINDER HEAD FOR INTERNALCODIBUS- 1 TION ENGINES Alfred Schwarz Montclair, N. J. I

. Application July'22,11936, Serial No. 92,047 r 3 Claims.

It is the object of the present invention toconstruct a cylinder head toconform with the ther mal requirements of the engine, particularly forhigh compression ratios, and combinetherewith structural stability.

Heat transfer and structural design are inseparable in an internalcombustion engine, particularly so in high speed engines where the timeelement is limited for acertain necessary amount of radiation. The totalradiation area is also limited for a given sized motor, as is thecubical content of the cylinder headfor a given compression ratio. Allof the factorsmust be coordinated with the type of metal used for theconstruction of the cylinder head, because of the widely varying heattransfer abilities of different metals. i r I It is the object of thepresent invention to de-' sign. a cylinder head, transferring the properamount of heat into the cooling medium during the various parts of thecycle, and yet maintaining the structural stability necessary to with--stand the explosion pressure,

In co-pending application No. 680,365 filed July' 14, 1933, I havedescribed a method of heat balancing cylinder heads, to correct alimitation of compression ratios which I-have determined experimentally.In which experiments I have found that compression ratios are limited bythe hottest and coolest portions of the cylinder'head.

It has been found that maximum compression, which as is well known willgive maximum power and economy, can onlybe obtained if the'cylinder headis substantially of uniform temperature. Such temperature islimit'ed-tobelow the auto-ignition temperatures of theparticular fuel used.

It had been determined previously that different sections of standardcylinder headsv difiered more than one hundred-degrees, even duringextended continuous operation, and that auto-ignition took place in'hotter sections, while the cooler sections caused a secondarydetonation,due to a delay in burning up to a period where abroadly developedflame-front set off the remaining charge too fast. Uniform temperaturesestablished in accordance with my previous application, permittedincreased compression ratio, and as a result, increased power andeconomy were obtained. It became a diflicult matter to obtain maximumresults with a metal of high heat con. ductivity, because the mostdesirable minimum cross sections caused structural weakness;

The present invention contemplates to use sections of the cylinder headwhich require greater cross sections for heat balancing purposes, alsofor structural purposes, and where such is not permissible,reinforcements "are used, and are. so designed as to maintain thedesired radiation capacity or heat storage, as the case may be. Y 6 Asis generally known, aluminum is a metal of high heat conductivity andoftenused for .cylinder heads. For the purpose of an example, I willassume that the-head is to be made from aluminum, in which case some ofthe sections re- 10 quired for proper heat balance and radiationcapacity are not sufiiciently strong to withstand the explosionpressure, which in gasoline engines is approximately 500 lb; persq.-inoh, .and the average area of a cylinder head may be taken as 15.15 sq. inches, so that thetotal explosion pressure ex-I erted againstthe cylinder head will is somewhere around 6000lbs.

' Referring now to the drawings there follows below a description ofthefigures thereof: 0 Fig. 1 is a fragmentary sectional view ofa castiron plate for use as a cylinder'head. v

, Fig.2 is a view similar to that ofe-Fig. 1, but

showing an aluminum plate. I

Fig. 3 is a sectional view through a portion of 25 a cylinder'head. 7 v

Fig. '4 is a sectional view of a cylinder head taken on line A-A of Fig.'5. i

Fig; 5 is abottom plan view of the cylinder, head of Fig. 4. w i

'FigQG is a plan view of thecylinder head viewed from thecombustion-chamber side, with the cylinder location'indicated by adotted line.

Fig. '7 is a plan View showing a 'cylinder'head for use on a fourcylinder motor;

Most metals, particularly aluminum, fatigue with age, and become weakerunder increased temperatures, so that it is-hotuncommon for aluminumcylinder heads to break, althoughtheoretically they may be designed towithstand 40 the pressure. Since it is desirable to use alum'inum as awall for the'combustion chamber, the present invention contemplates touse a' fairly heavy steel to formthe water 'jacketand to reinforce thealuminum combustion chamber plate in such sections'where'increasedheatstorage is desirable, and to reinforce the aluminum platein such places where increased sectionsare not permissible, byconnections to the water jacket coverplate so designed to maintain theproper radiation, as far as the combustion iscoricern'ei-and to obtainthe increased necessary strength by making said cover plate ofsufllcient strength and suitable design to carry the extraload. Wetherefore have the. heat balanced combustion of heat transfer from gasto metal, and metal to;

water, also taking into consideration the conductivity factor'of themetal. The cast iron plate Fig. No. 1, having a gas at a temperature of1500". F. on one side, and on that side, the surface temperature will be310 F. The mean temperature will be 265 F., and the water tem, peratureistaken as 160 F., which'is standard in gas engine testing practice.Under such conditions the heat transferfrom the gas to the water will be77,000 B. t. u. per hour per sq. it. while the heat storage is 1320 B t..u. at an intake temperature of 100. It I v Fig. No. 2 shows analuminumplate of the same thickness, and under the sameidentical condition theheat throughput is 80,900 B. t. u. per hour per sq. ft. -.The meantemperature is 240 F. The inner surface temperature is 250 F.', and thesurface exposed to the water is 230 F.

The heatstorage per sq. ft; is 785 B. t. u.

Comparing the two conditions we have in cast iron, a flow of heat of 310F. to 220 F. through which is adifierential of 90 F., while in thealuminum plate we have for the samethickness, only a differential of 20R, which indicates that the flow in the direction of AA in iron is muchslower than in aluminum. In other words all the, sections of an-aluminum cylinder head will bemore uniforma 'I'heheatretention capacityof aluminum is much smaller than iron, namely, only 785 B. t. u. per sq.ft. thick, while it is 1320 B. t.'u. for castiron. Ashas been seenbefore, the heat throughput through aluminum is much greater, andthis'latter fact would indicate a lower thermal efliciency for thealuminum head. However, looking at Fig. No. 3, which represents a crosssection of the charge of an L headmotor, we find that space A has a muchgreater capacity than space B. It standsto reason therefore that.the'wall section over A is heated much more than the section over B.Since every combustible only ignites when its heat of ignition isreached, section A will burn faster than section B, which causes asecondary explosion in section B, which assumes the proportion ofdetonation.

-'-I place over section B a greatermetal thickness, thereby increasingthe heat storage in the metal, giving some heat back to the new chargeduringcompression. The shock wall C having been foundby measurementsalways to be the hottest, .made-of' a particularly thin section. Theexhaust valve region is always hotter than the intake valve regiomand Itherefore decrease the section over the exhaust valve, and increase sameover the intake valve. All of this can be readily determined by takingreadings with constantan iron thermal couplesembedded into the cylinderhead wall. Suchreadings will only have to be taken once for a specificengine to determine the best cylinder head design.

Actual brake H. P. tests have shown beyond any question that a verymaterial increase in H. P. is obtained with the above described cylinatNo. 3 the thickness is A,.

der head design. The drawings show as follows: Fig. No. 4 shows a crosssection through the cylinder head AA. Fig. No. 5 shows a plan view ofone cylinder and valve chest from the side of the water jacket. Fig. No.6 shows a plan view of the cylinder head from the combustion chamberside, with the cylinder location indicated by a dotted line. Thedimensions in Fig. No. 4 will give the required wall thickness overvarious sections for an aluminum casting. At No. l the wall thickness is1 at No. 2 the thickness is In Fig. No. 5 it will be noted that the {athickness is carried on from No. 4 to No. 5 and is connected to thestud- I bolt bosses 6, 6, and 6. Fig. No. 4 shows reinsection againstthe heavy steel plate No. 8. No. 9 is another reinforcement post alsobraced against the steel plate No. 8. These reinforcement posts are socalculated in sections, that the increased heat at No. 10 is'dissipatedby increased area at No. 11. ply to a specificmotor only."

In the plan view, the reinforcement posts 1, 9, and. I2 are shown. Itmay be noted that the maximum span between reinforcements is therebyreducedto carry the explosion pressure, without however disturbing theheat balance of the cylinder head. Spark plug boss No, 13 also acts as areinforcement. It must be remembered that the stud bolts exerting eachabout 1500 lbs. pressure, and in the particular cylinder head covering 4cylinders illustrated in Fig. No. 7 there are stud bolts which are morethan ample to hold down theentire cylinder head and lend strength to thereinforced sections, each stud bolt being connected by ribs No. 14 tothe combustionchamber. e It isof course understood that various metalsmay be used for the combustion chamber plate,

providing the proper heat balance which is dif-,

ferent for different engines is taken into consideration. The method ofcalculating, hereinbefore given, can be usedby those versed in the artto design such cylinder heads. The cover plateNo. 8 forming the waterjacket may be either made from a flat sheet, or may itself be reinforcedwith ribs, without departing from .the invention.

I claim: l

1. A cylinder head for internal combustion engine cylinder blocks, saidhead having a wall constructed to provide any number of combustionchamber. wallportions to overlie the cylinders and their respectiveintake and exhaust valve ports in said block, each combustion chamberwall portion of said head being divided into areas of differential heattransfer capacity, the areas of greater heat transfer capacity beingarranged to overlie the hottest portions of the combustion chamber andbeing of less'tensile strength than Above dimensions obviously ap-' wallportion of said head being divided into areas overlying the intakeandexhaust port regions which are of different tensile strength and heattransfer capacity, and heat conducting means connected .to 'andreinforcing the area of lesser tensile strength and greater heattransfer capacity above the exhaust valve port of the block, wherebysubstantially unifornr icombustion wall strength and temperature duringthe power stroke of the engine is maintained.

3. A head for an internal combustion engine cylinder block, said headhaving a combustion chamber forming wall overlying the cylinder andintake and exhaust valve ports for said cylinder in said block, saidwall being divided into areas of differential heat transfer capacity,the area of

